Why I still reach for test-driven development

Test-driven development gets caricatured as writing tests for the sake of a coverage number. That's never been why I do it. I write the test first because it forces me to describe the behavior I actually want before I get seduced by an implementation.

The loop is simple: write a failing test, make it pass with the least code that works, then refactor with the test holding the shape in place. What surprises people is how much this changes the design, not just the correctness.

What TDD actually buys you

Three things, in my experience. First, smaller units — code that's hard to test is usually code that's doing too much. Second, a living spec: the tests describe intent far better than a stale wiki page. Third, fearless refactoring, which is the real unlock on long-lived systems.

Is it always worth it? No. Throwaway spikes and exploratory prototypes don't need it. But for anything that has to survive contact with production, I still start with the test.